* Made Serial API open the UART in NON BLOCKING mode
* Updated voxl_esc driver to latest from ModalAI fork
* Ported voxl_esc driver over to new Serial UART API
* Removed voxl_esc serial abstraction since new Serial API is already a serial abstraction
- Added an empty constructor, setPort, and validatePort functions for Serial API
- Changed GPS to not allocate Serial object dynamically
- Moved access check on serial port name into the Serial API
- Improved the Qurt platform validatePort Serial function to implement a more rigorous check. Added safety check
to the setPort Serial function to make sure it isn't called after the port has been already opened.
